Abradable labyrinth tooth seal

ABSTRACT

A seal assembly ( 52, 54 ) for a gas turbine engine ( 10 ). The seal assembly ( 52, 54 ) includes a first seal member ( 40 ) including an abradable structure having at least first and second seal portions ( 58, 64 ) radially spaced from each other, and a second seal member ( 44 ) including first and second seal surfaces ( 56, 62 ) located in facing relationship to the first and second seal portions ( 58, 64 ), respectively. The first seal member ( 40 ) is formed of a honeycomb structure, and the first seal portion ( 58 ) of the first seal member ( 40 ) is a thin fin-like structure having a width in the axial direction of the turbine engine ( 10 ) that is less than the width of the second seal portion ( 64 ) in the axial direction.

FIELD OF THE INVENTION

This invention relates in general to seals for multistage rotarymachines and, more particularly, to a seal assembly in a multistagerotary machine for providing interstage leakage control.

BACKGROUND OF THE INVENTION

In various multistage rotary machines used for energy conversion, suchas turbines, a fluid is used to produce rotational motion. In a gasturbine, for example, a gas is compressed through successive stages in acompressor and mixed with fuel in a combustor. The combination of gasand fuel is then ignited for generating combustion gases that aredirected to turbine stages to produce the rotational motion. The turbinestages and compressor stages typically have stationary or non-rotarycomponents, e.g., vanes, that cooperate with rotatable components, e.g.,rotor blades, for compressing and expanding the operational gases.

Any fluid leakage between stages reduces overall gas turbine engineperformance and efficiency and therefore, interstage seals in sealhousings are provided to reduce such leakage. In general, fluid leakageis reduced when the gap between the seal and a rotor assembly isminimized. Labyrinth seals have been used to effect a seal betweenstages at different pressures in gas turbine engines. Such sealsgenerally comprise two principal elements, i.e., a rotating seal and astatic seal. The static seal, as viewed in cross section parallel to theaxial length of the engine, frequently has rows of thin labyrinthfingers or teeth, typically formed of stainless steel, extendingradially from a relatively thicker base. The teeth of the static sealextend radially to a location adjacent the rotating seal. If contactoccurs between the labyrinth teeth and the rotating seal, the stainlesssteel teeth may harden, and wire-like strips of the tooth material maybe liberated from the labyrinth teeth. These so called “seal wires”enter the flow path and may cause significant damage to diaphragmairfoils, often resulting in forced outages to repair the damage.Accordingly, labyrinth seals have generally been designed to allowsufficient clearance to avoid problems associated with contact betweenthe labyrinth teeth and the adjacent seal surfaces, allowing a certainamount of leakage with an associated loss of performance.

It is also known to form the static seal or stator with a honeycombconfiguration for cooperating with a rotating seal component, such as arotary seal arm having a plurality of sharp seal teeth. These principalelements are positioned with a small radial gap therebetween to permitassembly of the rotating and static components. When the gas turbineengine is operated, the rotating seal expands radially more than thestatic seal and rubs into the static seal. The thin honeycombconstruction of the static seal reduces the surface area on which theseal teeth rub and thus helps to minimize the heat transferred into therotating seal.

It is an object of the present invention to provide a seal constructionfor a multistage rotary machine that does not require teeth to form aseal between stationary and rotating seal components. It is a furtherobject of the invention to provide such a seal construction in which agap between seal components may be reduced, and in which heat producedby abrading contact between such components may be minimized.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a seal assembly isprovided for a rotary machine having a stationary portion and arotatable portion. The seal assembly comprises a first seal membercomprising a honeycomb structure, and a second seal member comprisingfirst and second seal surfaces wherein the second seal surface isradially spaced from the first seal surface. The first seal memberincludes a first seal portion located in facing relationship to thefirst seal surface to form a seal therebetween, and a second sealportion located in facing relationship to the second seal surface toform a seal therebetween. The first seal portion defines a width in anaxial direction of the rotary machine that is less than the width of thesecond seal portion in the axial direction.

In accordance with a further aspect of the invention, a seal assembly isprovided for a rotary machine having a stationary portion and arotatable portion. The seal assembly comprises a first seal membercomprising an abradable structure having at least first and second sealportions radially spaced from each other, and a second seal membercomprising first and second seal surfaces located in facing relationshipto the first and second seal portions, respectively. The first sealportion defines a width in an axial direction of the rotary machine thatis less than the width of the second seal portion in the axialdirection.

In accordance with another aspect of the invention, a seal assembly isprovided for a rotary machine having a stationary portion and arotatable portion. The seal assembly comprises a first seal membercomprising a honeycomb structure having at least a first seal portion,and a second seal member located for seal engagement with the first sealportion of the first seal member. The first seal portion defines a widthin an axial direction of said rotary machine comprising approximatelytwo or less rows of cells of the honeycomb structure.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the present invention, it is believed that thepresent invention will be better understood from the followingdescription in conjunction with the accompanying Drawing Figures, inwhich like reference numerals identify like elements, and wherein:

FIG. 1 is a cross-sectional side view of a portion of a compressor for agas turbine engine incorporating the seal assembly of the presentinvention;

FIG. 2 is an enlarged view of area A in FIG. 1; and

FIG. 3 is an enlarged cross-sectional side view of an abradable surfaceof a first seal member for the seal assembly.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiment,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, a specific preferred embodiment in which the invention maybe practiced. It is to be understood that other embodiments may beutilized and that changes may be made without departing from the spiritand scope of the present invention.

Further, although the present invention may be applicable to variety ofrotary machinery, such as gas or steam turbines, compressors, etc., itwill be described with reference to a gas turbine engine 10, a portionof which is illustrated in FIG. 1. In particular, the portion of the gasturbine engine 10 illustrated in FIG. 1 comprises a compressor portionof the turbine engine 10.

FIG. 1 illustrates two compressor blades 12, 14 connected to respectiverotor disks 16, 18 of a rotor assembly supported for rotation about arotational axis (not shown) of the gas turbine engine 10. A vane 20 isconnected to the stationary casing 21 of the turbine engine 10 betweenthe two compressor blades 12, 14, and the compressor blades 12, 14 mayrotate relative to the vane 20 about the rotational axis of the turbineengine 10.

Referring to FIG. 2, the vane 20 includes an inner platform or innershroud 22 comprising an upstream or front edge 24 defining a frontannular spigot 26 and a downstream or rear edge 28 defining a rearannular spigot 30. A seal carrier 32 is supported radially inwardly fromthe vane 20 extending between the front and rear edges 24, 28 of theinner shroud 22. The seal carrier 32 includes a front flange portion 34engaged with the front spigot 26, and a rear flange portion 35 engagedwith the rear spigot 30 to thereby suspend the seal carrier 32 in closeproximity to the rotor disks 16, 18.

An upstream lower edge 36 of the seal carrier 32 is depicted herein asbeing radially displaced from a downstream lower edge 38. However, itshould be understood that the particular configuration of the sealcarriers 32 provided in the turbine engine 10 may vary, depending on thelocation of a particular seal carrier 32 along the axial length of theturbine engine 10.

The seal carrier 32 supports one or more first seal members, representedby an upstream first seal member 40 and downstream seal member 42 forcooperating with respective upstream and downstream second seal members44, 46. The upstream and downstream second seal members 44, 46 areformed on rotor arms 48, 50 extending axially from the respective rotordisks 16, 18. The upstream first and second seal members 40, 44 definean upstream seal assembly 52 and the downstream first and second sealmembers 42, 46 define a downstream seal assembly 54. The upstream anddownstream seal assemblies 52, 54 comprise substantially similarconstructions and are representative of the seal assemblies that may beprovided throughout the turbine engine 10. Further description of theseal assemblies 52, 54 will be provided with particular reference to theupstream seal assembly 52, it being understood that the downstream sealassembly 54 has substantially similar elements facing in an axiallyopposite direction.

The second seal member 44 comprises an annular or cylindrical first sealsurface 56, extending in the axial direction of the turbine engine 10.The first seal surface 56 is substantially smooth and defines agenerally continuous cylindrical surface facing radially outwardlytoward the first seal member 40. The first seal member 40 includes afirst seal portion 58 located in facing relationship to the first sealsurface 56 to define an outer seal location 66 for preventing orlimiting passage of gases flowing in the axial direction.

The second seal member 44 further comprises a radially extending,relatively narrow rim portion 60. The rim portion 60 defines a steppedstructure extending radially outwardly from the radial location of thefirst seal surface 56 and is shown located adjacent an end of the rotorarm 48. The rim portion 60 is substantially smooth and comprises agenerally continuous cylindrical second seal surface 62 facing radiallyoutwardly. The second seal surface 62 is located facing relationshiptoward a second seal portion 64 on the first seal member 40 to define aninner seal location 68.

The first and second seal surfaces 56, 62 of the second seal member 44are located in spaced relation but closely adjacent to the first andsecond seal portions 58, 64 of the first seal member 40 to define therespective inner and outer seals 66, 68 for limiting passage of gasestherethrough. As the turbine engine 10 is started up and reachesoperating speed, the rotor arm 48 may move radially outwardly, closingthe gap between the first and second seal members 40, 44. In an initialoperating period after installation of the first seal member 40, thereis a rub-in event during which the radial movement of the rotor arm 48may cause the first and second seal surfaces 56, 62 of the second sealmember 44 to contact the first and second seal portions 58, 64 of thefirst seal member 40, rubbing away or abrading pinch points of the firstand second seal portions 58, 64 where they come in contact with therespective first and second seal surfaces 56, 62.

The rub-in event establishes a close operating clearance, or minimalsealing gap between the first and second seal members 40, 44. Duringsubsequent operation of the turbine engine 10 following the rub-inevent, the first and second seal members 40, 44 will generally remain inclose, non-touching relation to each other during steady-stateoperation.

Referring additionally to FIG. 3, the first seal member 40 is preferablydefined by a honeycomb structure 67 attached to backing plate 69. Thehoneycomb structure 67 comprises a plurality of cells 70, each cell 70having a longitudinal dimension extending radially from the seal carrier32 and having an open end. The open ends of the cells 70 define thefirst and second seal portions 58, 64 located adjacent the first andsecond seal surfaces 56, 62 of the second seal member 44. The first sealportion 58 of the first seal member 40 comprises a fin-like structure atan outer edge 76 of the honeycomb structure 67, and is defined by alimited number of cells of the honeycomb structure 67, identified as 70a, extending a width X in the axial direction. Preferably, the width Xof the first seal portion 58 comprises a narrow honeycomb width definedby approximately two rows of cells 70 a in order to maintain structuralintegrity of the first seal portion 58. Due to the interfittingarrangement of the cells 70 of the honeycomb structure 67, the totalwidth of the first seal portion 58 is approximately equal toone-and-a-half times the diameter of a cell 70 a in the first sealportion 58, as measured in the axial direction between an inner edge 74and the outer edge 76 of the first seal portion 58. Accordingly, theseal width comprising two cell rows provides a series of interconnectedcomplete cells 70 a around the annular area comprising the first sealportion 58.

The fin-like portion of the honeycomb structure 67 defined by the firstseal portion 58 provides a relatively small or minimal annular surfacearea extending axially inwardly from the second seal portion 64 forengaging the first seal surface 56. Contact between the first sealportion 58 and the first seal surface 56 during the rub-in event mayabrade the portion of the honeycomb structure 67 defining the first sealportion 58 to define a minimal clearance area at the outer seal location66 during steady state operation of the turbine engine 10. The smallengagement area between the first seal portion 58 and first seal surface56 reduces the amount of material abraded from the first seal portion 58and also reduces the heat produced during the rub-in event.

The second seal portion 64 defines a surface on the first seal member 40having a width in the axial direction that is relatively wider than thewidth X of the first seal portion 58. However, the width of the secondseal surface 62 on the rim portion 60 of the rotor arm 48 is relativelynarrow in comparison to the portion of the rotor arm 48 defining thefirst seal surface 56. The second seal surface 62 presents a limitedannular area for contacting an area of the second seal portion 64. Thearea of the second seal portion 64 contacted by the second seal surface62 may be abraded during the rub-in event to define a small clearancearea at the inner seal location 68 between the second seal portion 64and the second seal surface 62.

Thermal effects in the turbine engine 10 may cause relative axialdisplacement between the second seal member 44 defined on the rotor arm48 and the first seal member 40 supported on the stationary inner shroud22, where the amount of axial travel is dependent on the particularaxial location of the seal assembly in the turbine engine 10. The widerportions of the outer and inner seal locations 66, 68, i.e., the firstseal surface 56 and the second seal portion 64, are preferably wideenough to accommodate axial travel of the second seal member 44 relativethe first seal member 40 during operation of the turbine engine 10.

The radial distance of the first seal portion 58 from the second sealportion 64 is substantially equal to the radial distance of the secondseal surface 62 from the first seal surface 56. Consequently, theinitial clearance between the first seal portion 58 and the first sealsurface 56 prior to the rub-in event is substantially the same as theinitial clearance between the second seal portion 64 and the second sealsurface 62. During the rub-in event, the first and second seal portions58, 64 are both abraded by the respective substantially smooth surfaces56, 62 of the second seal member 44 without producing excessive heat inthe first and second seal members 40, 44. That is, each of the first andsecond seal surfaces 56, 62 described herein are provided as non-toothedsurfaces for cooperating with the respective first and second sealportions 58, 64 defined on the honeycomb structure 67. Further, duringtransient rotational and thermal conditions that may occur duringoperation of the turbine engine 10, the first and second seal portions58, 64 will accommodate further contact with the first and second sealsurfaces 56, 62 by abrading at pinch points between the stationary androtating components.

The honeycomb structure 67 forming the first seal member 40 describedherein is preferably constructed of a corrosion resistant material. Inthe embodiment described herein the honeycomb structure 67 is formed ofa nickel-based alloy, such as HASTELLOY®. The first seal member 40 maybe attached to the seal carrier 32 by any conventional attachmentmethod. For example, the first seal member 40 may be welded or brazed tothe seal carrier 32.

Since the described seal assembly provides a thin fin-like seal portionof the honeycomb structure 67, as defined at the first seal portion 58,and does not require seal teeth formed on the cooperating rotor armsurface 56, the first seal member 40 may be readily retro-fit toexisting turbine engines 10 to cooperate with rotor arms havingsubstantially smooth seal surfaces

It should be understood that, within the scope of the present invention,one or more surfaces of the rotor arm 48 may be provided withalternative configurations for cooperating with the first seal member40. For example, the second seal surface 62 of the second seal member 44is not limited to the cylindrical surface illustrated for the presentdescription, and may comprise a very thin surface, e.g., a thin fin ortooth-like surface, for engaging a limited surface area of the opposingsecond seal portion 64.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A seal assembly for a rotary machine having a stationary portion anda rotatable portion, the seal assembly comprising: a first seal membercomprising a honeycomb structure; a second seal member comprising firstand second seal surfaces wherein said second seal surface is radiallyspaced from said first seal surface; said first seal member including afirst seal portion located in facing relationship to said first sealsurface to form a seal therebetween, and a second seal portion locatedin facing relationship to said second seal surface to form a sealtherebetween; and said first seal portion defining a width in an axialdirection of said rotary machine that is less than the width of saidsecond seal portion in the axial direction.
 2. The seal assembly ofclaim 1, wherein said first and second seal surfaces are eachsubstantially cylindrical surfaces, extending in the axial direction. 3.The seal assembly of claim 1, wherein the width of said first sealportion of said first seal member is less than the width of said firstseal surface.
 4. The seal assembly of claim 3, wherein the width of saidsecond seal portion is greater than the width of said second sealsurface.
 5. The seal assembly of claim 3, wherein the width of saidfirst seal portion is approximately equal to two rows of cells of saidhoneycomb structure.
 6. The seal assembly of claim 1, wherein said firstseal surface comprises a surface contacted by said first seal portionduring rotatable movement of said rotatable seal portion of said rotarymachine.
 7. The seal assembly of claim 6, wherein said first sealsurface is a non-toothed surface.
 8. The seal assembly of claim 1,wherein said second seal member comprises a rotor arm having a radiallyextending end portion, said radially extending end portion extendingfrom said first seal surface, and said second seal surface being definedon said end portion.
 9. The seal assembly of claim 8, wherein said firstseal member is mounted on a stationary seal carrier located radiallyoutwardly from said rotor arm.
 10. A seal assembly for a rotary machinehaving a stationary portion and a rotatable portion, the seal assemblycomprising: a first seal member comprising an abradable structure havingat least first and second seal portions radially spaced from each other;a second seal member comprising first and second seal surfaces locatedin facing relationship to said first and second seal portions,respectively; and said first seal portion defining a width in an axialdirection of said rotary machine that is less than the width of saidsecond seal portion in the axial direction.
 11. The seal assembly ofclaim 10, wherein said first seal surface is defined on a rotor arm andis located for engagement with said first seal portion.
 12. The sealassembly of claim 11, wherein said first seal portion comprises ahoneycomb structure.
 13. The seal assembly of claim 12, wherein saidfirst seal portion comprises approximately two or less rows of cells ofsaid honeycomb structure.
 14. The seal assembly of claim 1, wherein saidrotor arm includes a radially extending end portion, said radiallyextending end portion extending from said first seal surface, and saidsecond seal surface being defined on said end portion.
 15. The sealassembly of claim 14, wherein said abradable structure comprises ahoneycomb structure.
 16. The seal assembly of claim 10, wherein saidabradable structure comprises a honeycomb structure and said first andsecond seal surfaces are non-toothed surfaces.
 17. A seal assembly for arotary machine having a stationary portion and a rotatable portion, theseal assembly comprising: a first seal member comprising a honeycombstructure having at least a first seal portion; a second seal memberlocated for seal engagement with said first seal portion of said firstseal member; and said first seal portion defining a width in an axialdirection of said rotary machine comprising approximately two or lessrows of cells of said honeycomb structure.
 18. The seal assembly ofclaim 17, wherein said first seal member is mounted on a stationary sealcarrier member and said second seal member is defined on a rotor arm.19. The seal assembly of claim 18, wherein said second seal membercomprises first and second seal surfaces and said first seal memberfurther comprises a second seal portion defined by said honeycombstructure, said first seal surface forming a seal with said first sealportion and said second seal surface forming a seal with said secondseal portion.
 20. The seal assembly of claim 19, wherein said first sealportion and said first seal surface are radially displaced from saidsecond seal portion and said second seal surface, respectively.